The present invention relates to a method for arranging an optical module, in particular for a microlithography projection exposure system, in a measuring apparatus. Moreover, the invention relates to a measuring apparatus of this type and to a method for mounting an optical module in a projection exposure system for microlithography.
When producing a projection exposure system for microlithography individual optical modules of the projection exposure system are produced separately by the manufacturer, and are only fitted into the projection exposure system at the customer's premises. These types of separately produced optical modules can be e.g. illumination optics or a projection objective of the exposure system. Each of these optical modules comprises a series of optical elements which are adjusted in relation to one another by the manufacturer so that the optical characteristics of the module correspond to a target specification with a specific tolerance. The adjustment of the optical elements within the optical module takes place in an optical measuring apparatus. The optical module is then fitted in the projection exposure system at the client's premises. Here the optical module is generally disposed at a pre-specified position within the projection exposure system.
As already mentioned above, the actual optical characteristics of the module deviate from the target specification. In particular, the optical module to be fitted has an optical path the actual course of which within the optical module deviates from a desired course, so that during exposure operation of the projection exposure system an exit beam passing out of the optical module has a location and an orientation which deviate from a desired location and a desired orientation. It is therefore necessary to match the optical characteristics of the fitted optical module to the optical path of the projection exposure system. This is usually implemented by measuring optical parameters of the projection exposure system with the fitted optical module at the client's premises, and optimizing the latter by correspondingly adjusting optical elements of the projection exposure system. This adjustment process is very complex, however, and only enables optimization of the optical properties of the projection exposure system to a certain degree. The requirements for the optical quality of projection exposure systems are continuously becoming more and more stringent, however.